Use of the desmopressin test in the differential diagnosis of Pseudo-Cushing state from Cushing's disease
Giacomo Tirabassi, Emanuela Faloia, Roberta Papa, Giorgio Furlani, Marco Boscaro & Giorgio Arnaldi
Context: The desmopressin (DDAVP) test has been proposed to discriminate Cushings disease (CD) from Pseudo-Cushing states (PC); however, current information on its value is scarce and contradictory.
Objective: To assess the ability of the DDAVP test in distinguishing between these conditions, with emphasis on subjects with mild hypercortisolism.
Design: Retrospective/prospective study.
Setting: Division of Endocrinology, Polytechnic University of Marche, Ancona, Italy.
Patients: Fifty-two subjects with CD, 28 with PC and 31 control subjects (CT).
Intervention(s): DDAVP test and standard diagnostic procedures for the diagnosis of Cushings syndrome.
Main outcome measure(s): Diagnosis/exclusion of CD.
Results: Interpretation of the DDAVP test based on percent and absolute increment of cortisol and ACTH did not afford acceptable values of both sensitivity (SE) and specificity (SP). CD diagnosis based on simultaneous positivity for basal serum cortisol >331 nmol/l and absolute ACTH increment >4 pmol/l, and its exclusion in subjects negative for one or both measures, yielded an SE of 90.3% and an SP of 91.5%.
The approach was also highly effective in distinguishing PC from: i) CD with moderate values of urinary free cortisol (SE: 86.9%; SP: 92.8%); ii) CD with moderate values of serum cortisol after dexamethasone suppression (SE: 86.6%; SP: 92.8%); and iii) CD with moderate values of midnight serum cortisol (SE: 100%; SP: 92.8%).
Conclusions: Interpretation of the DDAVP test through a combination of parameters allowed effective discrimination of CD from PC even in subjects with mild hypercortisolism.